The present invention relates to a shock absorber control unit for use in a vehicle suspension, and more particularly to a unit for controlling a vehicle roll velocity which occurs when an operator drives a vehicle on a curved road.
In general, when an operator drives on a curved road as shown in FIG. 1 at a constant speed, the operator gradually rotates a steering wheel in the counterclockwise direction from a point B. FIG. 2(a) shows a rotated angle of a steering shaft when the vehicle runs through the points of the curved road as shown in FIG. 1. From this FIG. 2(a), it is apparent that the steering angle gradually varies from the point B. An operator will hesitate to rotate a steering wheel quickly in a direction because this will increase a vehicle's roll. When the operator drives through the curved road by the adequate steering operation, and reaches a point C, the operator rotates the steering wheel in the clockwise direction in order to straighten the vehicle. The operator can quickly rotate the steering wheel (e.g. the operator can rotate the steering wheel at a high steering angular velocity) at the point just past the point C to straighten the car as shown in FIG. 2(b).
Heretofore, a shock absorber control unit has been proposed such that it increases the damping force of the shock absorber when the steering angular velocity exceeds a predetermined value decided by the vehicle speed, and thereby decreases the vehicle roll. The proposed prior art shock absorber control unit is designed to increase the damping force of the shock absorber even when the operator returns the steering wheel from the turning position to the neutral position. FIG. 2(c) shows a degree of a vehicle roll, and the broken line in FIG. 2(c) indicates the degree of a vehicle's roll according to the proposed prior art. As apparent from the FIG. 2(c), the degree of the vehicle roll from the point C to the point D according to the prior art is almost same as that of the roll from the point B to the point C. This means that the vehicle receives a high roll even when the operator rotates the steering wheel in the direction from the turning position to the neutral position thereof. This performance results in the delay of the vehicle being returned to the normal attitude.